The present invention relates to building roofs, and more particularly, to thermal insulation therefor.
The ever increasing cost of energy forces building designers to become acutely aware of building insulation structure and the effectiveness thereof. A poorly insulated building can be costly in terms of heating and cooling expenses, as well as costly in terms of lost work hours due to employee discomfort.
In highrise buildings, it has been discovered that the major heat loss therefrom occurs from the walls, whereas in lowrise buildings, it has been found that the major heat loss occurs therefrom through the roof. Thus in lowrise buildings, roof design is a major consideration in building design, and the roof insulating means is a major element in controlling the overall energy costs of the lowrise building.
Known lowrise buildings have a roof insulating configuration formed of a single layer of insulation comprised of a plurality of panels of flexible insulation, such as glass fiber blankets, laid end-to-end and stretched over structural members, such as roof purlins, just prior to positioning and fastening the roof panels to the purlins. The single layer of insulation is compressed or pinched between the purlin and roof panel at each purlin, and the thus distorted insulation has a heat path therethrough having a thermal resistance which is reduced from a heat path through undistorted insulation, i.e., a "thermal weakness" exists adjacent the purlins. Accordingly, because of this "thermal weakness", much heat energy can be lost through the insulated roof at, or near, the purlins. Furthermore, in view of the need for efficient and effective building thermal designs, even at positions spaced from the purlins, a single layer of insulation may prove to be inadequate.
Simply increasing the thickness of the single layer of insulation does not provide a complete answer, as thick insulation is difficult to handle and this solution is not efficient enough to offset the problems attendant therewith. Furthermore, thick layers of insulation blankets may cause the fasteners used to connect the roof panels to the purlins through the insulation to dimple the roof panels, and possibly to become loosened after a period of time. Therefore, practical considerations limit roof insulation configurations to panels of 3 to 4 inches in thickness.
One construction which has been proposed for increasing the thermal resistance in the heat path adjacent the roof purlins, without increasing the thickness of the insulation blankets used, includes a thermal spacer block interposed between the insulation and the roof panel. The spacer block can be constructed of insulating material and does somewhat improve the thermal resistance of the heat path through the insulation adjacent the purlins. However, such a construction still utilizes only a single layer of insulation, and as insulation requirements continue to increase, even such spacer blocks will not provide a complete solution to the problems of providing adequate insulation in an economical and workable manner, and thus further solutions are required.
There is one structure proposed for insulating a building roof which includes a U-shaped cap member placed over a purlin to support an insulation panel. However, the insulation panel is still only a single layer thick and this single layer is pinched between the purlin and the roof. There is no compensation made for this reduced insulation thickness. Because of this, the thermal resistance of the insulation of this configuration is still inadequate to meet today's demand for efficient, economical and practical roof insulation.
Accordingly, the present invention provides an insulation configuration which includes a plurality of discrete layers of insulation which are separated at a purlin by a spacer channel.